The present invention relates to a multilayered apertured film wrapping element for an absorbent article. At least one outer layer of the fluid-impervious plastic material has a continuous phase of a thermoplastic polymeric component and an immiscible, dispersed phase of a thermoplastic polymeric component having a lower melting point. The wrapping element is useful in applications involving heat sealing and similar thermal processes in absorbent articles, such as sanitary napkins, diapers, bandages, tampons, and the like.
There are several types of wrapping elements, including covers, that have been or are currently in use for absorbent articles: woven fabrics, nonwoven fabrics, apertured films, reticulated films, polymer nets, and the like. There has been a progression from woven fabrics to nonwoven fabrics and apertured films in these covers. These covers are often adhesively attached to other components in the absorbent article. An adhesive may be applied as a separate component between the cover and another component, or adhesion may result from “heat sealing” or heating one of the components to cause it to become adhesive.
Nonwoven fabrics may incorporate multicomponent fibers having at least two different melting points. Then these fabrics may be adhered to an absorbent article, such as a tampon, as described in Friese, U.S. Pat. Nos. 4,816,100; 4,836,450; and 4,859,273. This is one example of heat sealing a wrapping element or cover.
It may also be desirable to heat seal an apertured film. While it may be possible to heat seal an apertured film that is formed of only one component, this is generally only in areas where it is acceptable or even desirable that the apertures in the film become closed. However, heat sealing an apertured film to an underlying fibrous structure in a manner that maintains open apertures in the heat sealing area is more complex, and it generally requires the use of a film material having at least two different components having at least two different melting point temperatures. An example of this is described in Thompson et al., U.S. Pat. No. 5,342,334. In this example, the apertured film is formed from a co-extruded film having a higher melting point polymeric material on a first, non-bonded surface, and a lower melting point polymeric material on a second, heat-bondable surface. Unfortunately, this arrangement provides a large surface area of bondable material on the second surface, and it may allow unwanted or overly aggressive adhesion in the manufacturing process or final product. The film may adhere to process equipment, such as the apertured film forming surfaces and heat sealing elements. In addition, both layers of the film are exposed to process equipment.
Therefore, what is needed is an apertured film that is heat sealable in a controlled manner, that maintains open apertures, that separates at least one intermediate layer of the film from process equipment to protect both the layer and the equipment from damage, and that allows improved balance of film properties over a monolayer or bilayer film.